1/21. Brain imaging in a patient with hemimicropsia.Hemimicropsia is an isolated misperception of the size of objects in one hemifield (objects appear smaller) which is, as a phenomenon of central origin, very infrequently reported in literature. We present a case of hemimicropsia as a selective deficit of size and distance perception in the left hemifield without hemianopsia caused by a cavernous angioma with hemorrhage in the right occipitotemporal area. The symptom occurred only intermittently and was considered the consequence of a local irritation by the hemorrhage. Imaging data including a volume-rendering MR data set of the patient's brain were transformed to the 3-D stereotactic grid system by Talairach and warped to a novel digital 3-D brain atlas. Imaging analysis included functional MRI (fMRI) to analyse the patient's visual cortex areas (mainly V5) in relation to the localization of the hemangioma to establish physiological landmarks with respect to visual stimulation. The lesion was localized in the peripheral visual association cortex, Brodmann area (BA) 19, adjacent to BA 37, both of which are part of the occipitotemporal visual pathway. Additional psychophysical measurements revealed an elevated threshold for perceiving coherent motion, which we relate to a partial loss of function in V5, a region adjacent to the cavernoma. In our study, we localized for the first time a cerebral lesion causing micropsia by digital mapping in Talairach space using a 3-D brain atlas and topologically related it to fMRI data for visual motion. The localization of the brain lesion affecting BA 19 and the occipitotemporal visual pathway is discussed with respect to experimental and case report findings about the neural basis of object size perception.- - - - - - - - - - ranking = 1keywords = motion (Clic here for more details about this article) |
2/21. Stress-related primary intracerebral hemorrhage: autopsy clues to underlying mechanism.BACKGROUND: research into the causes of small-vessel stroke has been hindered by technical constraints. Cases of intracerebral hemorrhage occurring in unusual clinical contexts suggest a causal role for sudden increases in blood pressure and/or cerebral blood flow. CASE DESCRIPTION: We describe a fatal primary thalamic/brain stem hemorrhage occurring in the context of sudden emotional upset. At autopsy, the brain harbored several perforating artery fibrinoid lesions adjacent to and remote from the hematoma as well as old lacunar infarcts and healed destructive small-vessel lesions. CONCLUSIONS: We postulate that the emotional upset caused a sudden rise in blood pressure/cerebral blood flow, mediating small-vessel fibrinoid necrosis and rupture. This or a related mechanism may underlie many small-vessel strokes.- - - - - - - - - - ranking = 1keywords = motion (Clic here for more details about this article) |
3/21. Interhemispheric transfer of visual motion information after a posterior callosal lesion: a neuropsychological and fMRI study.Interhemispheric transfer of visual information was investigated behaviourally and with functional magnetic resonance imaging (fMRI) 6 months after a lesion of the posterior two-thirds of the corpus callosum. On tachistoscopical left hemifield presentation, the patient was severely impaired in reading letters, words and geographical names and moderately impaired in naming pictures and colours. In contrast, interhemispheric transfer of visual motion information, tested by verbal report of the direction of short sequences of coherent dot motion presented within the left hemifield, was preserved. The pattern of cerebral activation elicited by apparent motion stimuli was studied with fMRI and compared to that of normal subjects. In normal subjects, apparent motion stimuli, as compared to darkness, activated strongly striate and extrastriate cortex. When presented to one hemifield only, the contralateral calcarine region was activated while regions on the occipital convexity, including putative area V5, were activated bilaterally. A similar activation pattern was found in the patient with a posterior callosal lesion; unilateral left or right hemifield stimulation was accompanied by activation in the contralateral and ipsilateral occipital convexity. Ipsilateral hemifield representation in the extrastriate visual cortex is believed to depend on callosal input. Our observation suggests that this is not the case for visual motion representation and that other, probably parallel, pathways may mediate visual motion transfer after posterior callosotomy.- - - - - - - - - - ranking = 5keywords = motion (Clic here for more details about this article) |
4/21. Visuospatial hemi-inattention following cerebellar/brain stem bleeding.Neglect is a unilateral lack of responsiveness to stimuli caused by visuospatial hemi-inattention, a unilateral representation deficit and/or a unilateral hypokinesia. It results most frequently from right-hemisphere brain damage, particularly of the parietal lobe but also of the frontal cortex, the basal ganglia, the thalamus, and recently it has also been described after a cerebellar lesion. We report a patient with right-sided bleeding of the posterior inferior cerebellar artery, who developed a left-sided visual hemi-inattention. She had no visual field defects, yet she had problems detecting left-sided targets in visual extinction. Furthermore, she was impaired in detecting complex motion on the left side and targets in a fixation offset paradigm. Reactions to left-sided targets in covert shifts of attention were slowed in the invalid condition. Her text reading was impaired as she could not always find the initial word of the next line. However, she was aware of her deficit. Her visuoconstructive ability was normal and she gave no indication of tactile or acoustic extinction. As the cerebellar lesion was located in the right hemisphere and the inattention involved the left side of space, we suggest that the damage to the right brain stem led to a transient imbalance of the noradrenergic ascending activation system which may explain her hemi-inattention.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
5/21. Increased regional cerebral blood flow in the contralateral thalamus after successful motor cortex stimulation in a patient with poststroke pain.The mechanisms underlying poststroke pain have not been clearly identified. Although motor cortex stimulation (MCS) sometimes reduces poststroke pain successfully, the exact mechanism is not yet known. For further investigation of the neural pathways involved in the processing of poststroke pain and in pain reduction by MCS, the authors used positron emission tomography (PET) scanning to determine significant changes in regional cerebral blood flow (rCBF). This 58-year-old right-handed man suffered from right-sided poststroke pain for which he underwent implantation of a stimulation electrode in the right motor cortex. After 30 minutes of stimulation, his pain was remarkably reduced (visual analog scale scores decreased 8 to 1) and he felt warmth in his left arm. The rCBF was studied using PET scanning with 15O-labeled water when the patient was in the following states: before MCS (painful condition, no stimulation) and after successful MCS (painless condition, no stimulation). The images were analyzed using statistical parametric mapping software. State-dependent differences in global blood flow were covaried using analysis of covariance. Comparisons of the patient's rCBF in the painful condition with that in the painless condition revealed significant rCBF increases in the left rectus gyrus (BA11), left superior frontal lobe (BA9), left anterior cingulate gyms (BA32), and the left thalamus (p < 0.05, corrected). On the other hand, there were significant decreases in rCBF in the right superior temporal gyrus (BA22, p < 0.01, corrected) and the left middle occipital gyrus (BA19, p < 0.05, corrected). The efficacy of MCS was mainly related to increased synaptic activity in the thalamus, whereas the activations in the rectus gyrus, anterior cingulate gyrus, and superior frontal cortex as well as the inactivation of the superior temporal lobe may be related to emotional processes. This is the first report in which the contralateral thalamus was significantly activated and pain relief was achieved using MCS.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
6/21. Cerebral processing in the minimally conscious state.We studied a patient in a minimally conscious state using PET and cognitive evoked potentials. Cerebral metabolism was below half of normal values. Auditory stimuli with emotional valence (infant cries and the patient's own name) induced a much more widespread activation than did meaningless noise; the activation pattern was comparable with that previously obtained in controls. Cognitive potentials showed preserved P300 responses to the patient's own name.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
7/21. Bilateral occipital-parietal hemorrhagic infarctions following chiropractic cervical manipulation.A 26-year-old woman presented with acute headache and hand-motion vision in both eyes. One day prior to presentation she went to her chiropractor for cervical manipulation. The patient had received 20 chiropractic manipulations over the previous two years. CT scan and MRI showed bilateral, symmetric occipital-parietal hemorrhagic infarctions. angiography revealed severe focal stenosis in the distal vertebral arteries bilaterally at the superior C1 level possibly representing dissections. There was also a pseudoaneurysm of the left vertebral artery at the C1 level. risk factors included chiropractic manipulation, recent fever, and therapies for polycystic ovarian disease. The patient showed slow, steady improvement in her vision. Twenty days following admission, vision was 20/20 OU. The improvement in her vision most likely reflects the reduction in swelling and absorption of blood at the site of the strokes.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
8/21. Specific retinotopically based magnocellular impairment in a patient with medial visual dorsal stream damage.We report here retinotopically based magnocellular deficits in a patient with a unilateral parieto-occipital lesion. We applied convergent methodologies to study his dorsal stream processing, using psychophysics as well as structural and functional imaging. Using standard perimetry we found deficits involving the periphery of the left inferior quadrant abutting the horizontal meridian, suggesting damage of dorsal retinotopic representations beyond V1. Retinotopic damage was much more extensive when probed with frequency-doubling based contrast sensitivity measurements, which isolate processing within the magnocellular pathway: sensitivity losses now encroached on the visual central representation and did not respect the horizontal meridian, suggesting further damage to dorsal stream retinotopic areas that contain full hemi-field representations, such as human V3A or V6. Functional imaging revealed normal responses of human MT to motion contrast. Taken together, these findings are consistent with a recent proposal of two distinct magnocellular dorsal stream pathways: a latero-dorsal pathway passing to MT and concerned with the processing of coherent motion, and a medio-dorsal pathway that routes information from V3A to the human homologue of V6. Anatomical evidence was consistent with sparing of the latero-dorsal pathway in our patient, and was corroborated by his normal performance in speed, direction discrimination and motion coherence tasks with 2D and 3D objects. His pattern of dysfunction suggests damage only to the medio-dorsal pathway, an inference that is consistent with structural imaging data, which revealed a lesion encompassing the right parieto-occipital sulcus.- - - - - - - - - - ranking = 1.5keywords = motion (Clic here for more details about this article) |
9/21. color Doppler flow imaging of CSF flow in an infant with intraventricular hemorrhage.Evaluation of CSF flow was performed by means of the color Doppler flow imaging (CDFI) technique. The motion of CSF was examined in an infant with intraventricular hemorrhage (IVH). With the aid of CDFI, CSF flow in the aqueduct, 3rd ventricle and foramen of Monro could be demonstrated. CSF flow in both upward and downward directions was clearly visualized, primarily reflecting cardiac pulsation and respiration. When he was subjected with intermittent positive pressure ventilation, during inspiration there was upward flow in the aqueduct, while during expiration there was downward flow. Our experience indicates that CDFI is a useful technique for examining the CSF circulation in infants with IVH.- - - - - - - - - - ranking = 0.5keywords = motion (Clic here for more details about this article) |
10/21. fluoxetine as a treatment for emotional lability after brain injury.Emotional lability or emotionalism is a relatively common phenomenon and frequently occurs following vascular or traumatic brain injury. It is distressing and embarrassing to sufferers and their families, and often interferes with rehabilitation. At present there is no satisfactory or reliable treatment for this condition. We describe an open trial using fluoxetine, a newer antidepressant with a specific serotonergic action, in the treatment of emotional lability due to brain injury. Six consecutive cases of emotional lability attending a rehabilitation unit were studied (five cases of cerebrovascular accident and one of traumatic brain injury). Response to treatment was measured using a modification of the scale described by Lawson and MacLeod [1]. All showed a marked improvement within one week of commencing fluoxetine and the drug was well tolerated with no reported side-effects. The speed of onset and degree of improvement suggest that fluoxetine may be a useful agent in the treatment of emotional lability due to brain injury. Our observations indicate that further investigation of the role of fluoxetine in the treatment of emotional lability is warranted.- - - - - - - - - - ranking = 5keywords = motion (Clic here for more details about this article) |
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